Sidewalls of electroplated copper interconnects

ABSTRACT

A structure formed in an opening having a substantially vertical sidewall defined by a non-metallic material and having a substantially horizontal bottom defined by a conductive pad, the structure including a diffusion barrier covering the sidewall and a fill composed of conductive material. The structure including a first intermetallic compound separating the diffusion barrier from the conductive material, the first intermetallic compound comprises an alloying material and the conductive material, and is mechanically bound to the conductive material, the alloying material is at least one of the materials selected from the group of chromium, tin, nickel, magnesium, cobalt, aluminum, manganese, titanium, zirconium, indium, palladium, and silver; and a first high friction interface located between the diffusion barrier and the first intermetallic compound and parallel to the sidewall of the opening, wherein the first high friction interface results in a mechanical bond between the diffusion barrier and the first intermetallic compound.

BACKGROUND

1. Field of the Invention

The present invention generally relates to integrated circuits, and moreparticularly to electroplating copper interconnects.

2. Background of Invention

Advancements in the area of semiconductor fabrication have enabled themanufacturing of integrated circuits that have a high density ofelectronic components. The length and number of interconnect wiringincreases in high density integrated circuits. Three-dimensional (3D)stacking of integrated circuits has been created to address thesechallenges. Fabrication of 3D integrated circuits includes at least twosilicon chips stacked vertically. Vertically stacked chips can reduceinterconnect wiring length and increase device density. Deepthrough-substrate vias (TSVs) can provide interconnections andelectrical connectivity between the electronic components of thevertically stacked chips. Such vias may require high aspect ratios,where the via height is large with respect to the via width, to savevaluable area on the silicon substrate. TSVs enable increased devicedensity while reducing the total length of interconnect wiring.

However, fabrication techniques such as chemical vapor deposition (CVD)are unable to fill high aspect ratio TSVs without the risk of pinch-off.Pinch-off refers to build up of deposited material at an opening of atrench or a via hole (e.g., TSV). Pinch-off can result in the formationof voids, where some volume of a trench or a via hole (e.g., TSV) remainunfilled with the deposited material. Void formation can reduce theconductive cross section and if large enough may constitute a short andsever the interconnect structure. Thus, void formation can reduceintegrated circuit performance, decrease reliability of interconnects,cause sudden data loss, and reduce the useful life of semiconductorintegrated circuit products. In addition, pinch-off can result inundesired process chemicals to be trapped within a trench or a via hole(e.g., TSV).

An alternative technique for filling TSVs with conductive material mayinclude electroplating. Electroplating techniques require a cathode. IFthe part to be plated is conductive, it can serve as the cathode. Thecathode can be connected to a negative terminal of an external powersupply and thus must be electrically conductive. A seed layer can bedeposited to serve as the cathode. For example, a copper film may bedeposited using physical vapor deposition or other known depositiontechniques to form the requisite cathode, or seed layer, in preparationfor electroplating. When electroplating a trench or via hole anelectrical potential is applied to the cathode while the structure isexposed to an electrolyte solution where the desired plating materialcan plate out onto the cathode. However, in high aspect ratio features,the risk of pinch-off remains because the deposition on sidewalls andbottom can proceed roughly at the same rate, so the feature closes fromthe sides before fully filling from the bottom (this tendency isexacerbated by mass transfer limitations at the remote end of a deepfeature).

Accordingly, current fabrication techniques for filling high aspectratio TSVs with a conductive material show risks and disadvantages.Despite achievements that have been made in 3D integrated circuittechnology, to increase device density and reduce the length ofinterconnection wiring, the challenge of fabricating and filling highaspect ratio TSVs without void formation and chemical entrapmentcontinues to persist.

SUMMARY

According one embodiment of the present invention, a structure formed inan opening, the opening having a substantially vertical sidewall definedby a non-metallic material and having a substantially horizontal bottomdefined by a conductive pad, the structure comprising a diffusionbarrier covering the sidewall and a fill composed of conductivematerial: is provided. The structure may include a first intermetalliccompound separating the diffusion barrier from the conductive material,wherein the first intermetallic compound comprises an alloying materialand the conductive material, and is mechanically bound to the conductivematerial, wherein the alloying material is at least one of the materialsselected from the group consisting of chromium, tin, nickel, magnesium,cobalt, aluminum, manganese, titanium, zirconium, indium, palladium, andsilver; and a first high friction interface located between thediffusion barrier and the first intermetallic compound and parallel tothe sidewall of the opening, wherein the first high friction interfaceresults in a mechanical bond between the diffusion barrier and the firstintermetallic compound.

According another exemplary embodiment, structure formed in an opening,the opening having a substantially vertical sidewall defined by anon-metallic material and having a substantially horizontal bottomdefined by the non-metallic material, the structure comprising adiffusion barrier covering the sidewall and bottom, and a fill composedof conductive material is provided. The structure may include a seedlayer located directly on top of and conformal to the diffusion barrier,wherein the seed layer is parallel to the sidewall and bottom of theopening; a first intermetallic compound separating the seed layer andthe conductive material and parallel to the sidewall of the opening,wherein the first intermetallic compound comprises an alloying materialand the conductive material, and is mechanically bound to the conductivematerial, wherein the alloying material is at least one of the materialsselected from the group consisting of chromium, tin, nickel, magnesium,cobalt, aluminum, manganese, titanium, zirconium, indium, palladium, andsilver; and a first high friction interface located between the seedlayer and the first intermetallic compound and parallel to the sidewallof the opening, wherein the first high friction interface results in amechanical bond between the seed layer and the first intermetalliccompound.

According another exemplary embodiment, a method of plating a structurecomprising an opening etched in a nonmetallic material, a diffusionbarrier deposited along a sidewall of the opening, and a conductive padlocated at a bottom of the opening is provided. The method may includedepositing an alloying material on top of the diffusion barrier, whereinthe alloying material comprises an incorrect crystalline structure toserve as a seed for plating the conductive material, exposing theopening to an electroplating solution comprising the conductivematerial, and applying an electrical potential to the conductive padcausing the conductive material to deposit from the electroplatingsolution onto the conductive pad and causing the opening to fill withthe conductive material. The method may further include forming a firstintermetallic compound along an intersection of the alloying materialand the conductive material, the first intermetallic compound comprisingthe alloying material and the conductive material,

According another exemplary embodiment, a method of plating a structurecomprising an opening etched in a nonmetallic material and a diffusionbarrier deposited along a sidewall and along a bottom of the opening isprovided. The method may include depositing a seed layer along thesidewall and the bottom of the opening, wherein the seed layer comprisesa correct crystalline structure to seed copper, depositing an alloyingmaterial on top of the diffusion barrier and parallel to the sidewall ofthe opening, wherein the alloying material comprises an incorrectcrystalline structure to serve as a seed for plating the conductivematerial, and exposing the opening to an electroplating solutioncomprising the conductive material. The method may further includeapplying an electrical potential to the seed layer causing theconductive material to deposit from the electroplating solution onto theseed layer exposed at the bottom of the opening and causing the openingto fill with the conductive material, and forming a first intermetalliccompound along an intersection between the alloying material and theconductive material, the first intermetallic compound comprising thealloying material and the conductive material.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The following detailed description, given by way of example and notintend to limit the disclosure solely thereto, will best be appreciatedin conjunction with the accompanying drawings, in which:

FIGS. 1A-1D illustrate the steps of a method of forming a copperinterconnect structure according to one embodiment.

FIG. 1A illustrates a step in the formation of a copper interconnectstructure according to one embodiment.

FIG. 1B illustrates a step in the formation of a copper interconnectstructure according to one embodiment.

FIG. 1C illustrates a step in the formation of a copper interconnectstructure according to one embodiment.

FIG. 1D illustrates a step in the formation of a copper interconnectstructure according to one embodiment.

FIG. 2 illustrates a copper interconnect structure according to oneembodiment.

FIG. 3 illustrates a copper interconnect structure according to oneembodiment.

FIG. 4 illustrates a copper interconnect structure according to oneembodiment.

FIG. 5 illustrates a copper interconnect structure according to oneembodiment.

FIG. 6 illustrates a copper interconnect structure according to oneembodiment.

FIG. 7A-7E illustrate the steps of a method of forming a copperinterconnect structure according to one embodiment.

FIG. 7A illustrates a step in the formation of a copper interconnectstructure according to one embodiment.

FIG. 7B illustrates a step in the formation of a copper interconnectstructure according to one embodiment.

FIG. 7C illustrates a step in the formation of a copper interconnectstructure according to one embodiment.

FIG. 7D illustrates a step in the formation of a copper interconnectstructure according to one embodiment.

FIG. 7E illustrates a step in the formation of a copper interconnectstructure according to one embodiment.

FIG. 8 illustrates a copper interconnect structure according to oneembodiment.

FIG. 9 illustrates a copper interconnect structure according to oneembodiment.

FIG. 10 illustrates a copper interconnect structure according to oneembodiment.

FIG. 11 illustrates a copper interconnect structure according to oneembodiment.

FIG. 12 illustrates a copper interconnect structure according to oneembodiment.

FIG. 13 illustrates a copper interconnect structure according to oneembodiment.

FIG. 14 illustrates a copper interconnect structure according to oneembodiment.

The drawings are not necessarily to scale. The drawings are merelyschematic representations, not intended to portray specific parametersof the invention. The drawings are intended to depict only typicalembodiments of the invention. In the drawings, like numbering representslike elements.

DETAILED DESCRIPTION

Detailed embodiments of the claimed structures and methods are disclosedherein; however, it is understood that the disclosed embodiments aremerely illustrative of the claimed structures and methods that may beembodied in various forms. This disclosure may, however, be embodied inmany different forms and should not be construed as limited to theexemplary embodiment set forth herein. Rather, these exemplaryembodiments are provided so that this disclosure will be thorough andcomplete and will fully convey the scope of this disclosure to thoseskilled in the art. In the description, details of well-known featuresand techniques may be omitted to avoid unnecessarily obscuring thepresented embodiments.

Referring to FIGS. 1A-1D, multiple steps of a method of forming aninterconnect structure are shown. Now referring to FIG. 1A, across-sectional view of an interconnect structure 100 having an opening106 in a nonmetallic material 102 and a conductive pad 104 positioned ata bottom 108 of the opening 106 is shown. The interconnect structure 100may include lines, wires, vias or through-substrate vias (TSVs). In oneembodiment, the nonmetallic material 102 may be made from any of severalknown semiconductor materials such as, for example, silicon (e.g. a bulksilicon substrate), germanium, silicon-germanium alloy, silicon carbide,silicon-germanium carbide alloy, and compound (e.g. III-V and II-VI)semiconductor materials. In one embodiment, the nonmetallic material 102may be made from any dielectric material know to a person havingordinary skill in the art. The conductive pad 104 itself may include aline, a wire or a via. Alternatively, the interconnect structure 100 mayinclude a trench formed in the nonmetallic material 102 without theconductive pad 104, as described below (see FIGS. 7A-7E, 8-12). Anoptional electrically insulating liner 110 (not shown) may be depositedalong a sidewall 109 of the opening 106 and on top of the nonmetallicmaterial 102.

Now referring to FIG. 1B, a diffusion barrier 112 may be deposited alongthe sidewall 109 of the opening 106 and on top of the nonmetallicmaterial 102. The diffusion barrier 112 may be deposited only on thenonmetallic material 102 and not on the conductive pad 104. Thediffusion barrier 112 may include any material that which prohibitscontamination of a copper material by the nonmetallic material 102. Inone embodiment, the diffusion barrier 112 may be made from a materialincluding tantalum nitride deposited by physical vapor deposition (PVD).In one embodiment, the diffusion barrier 112 may be deposited by analternative deposition technique, for example chemical vapor deposition(CVD) or atomic layer deposition (ALD).

Now referring to FIG. 1C, an alloying material 114 may be deposited ontop of the diffusion barrier 112. In one embodiment, the alloyingmaterial 114 may be deposited only on the diffusion barrier 112 and noton the conductive pad 104. In one embodiment, the alloying material 114may be made from a material including chromium deposited in a vacuumusing a sputter deposition technique. In one embodiment, the alloyingmaterial 114 may be made from a material including chromium, copper,nickel, tin, magnesium, cobalt, aluminum, manganese, titanium,zirconium, indium, palladium, gold, or some combination thereof. Thealloying material 114 may not have the correct crystalline structure toserve as a seed for copper plating. In other words, the crystal faceorientation of the alloying material 114 may not mimic the crystal faceorientation of copper; such that the surface of the alloying material114 will not allow copper to grow from the its face. For example, Cr hasa BCC (Body Centered Cubic) lattice whereas Cu has an FCC (Face CenteredCubic) lattice. These two lattice structures are inherentlyincompatible, i.e. Cr cannot act as a seed for Cu plating.

In one embodiment, an optional adhesive liner 128 such as gold (see FIG.13) may be used prior to depositing the alloying material 114. Thealloying material 114 may have a thickness ranging from about 50angstroms to about 300 angstroms.

In one embodiment, the diffusion barrier 112 and the alloying material114 may be deposited on the sidewall 109 and the bottom 108 of theopening 106. In such embodiments, the diffusion barrier 112 and thealloying material 114 may be subsequently removed from the bottom 108 ofthe opening 106. For example, an anisotropic etch may be used to removethe diffusion barrier 112 and the alloying material 114 from the bottom108 to expose the conductive pad 104 without removing the diffusionbarrier 112 and the alloying material 114 from the sidewall 109 of theopening 106. This anisotropic etch may be performed after all layers aredeposited or immediately following the deposition of each layer.

Now referring to FIG. 1D, a copper material 116 may be deposited on theconductive pad 104 within the opening 106 (shown in FIG. 1C) using anelectroplating technique. The conductive pad 104 may serve as a cathodeto which an electrical potential is applied during the electroplatingtechnique. Specifically, a negative voltage may be applied to theconductive pad 104. The conductive pad 104 may also serve as a copperseed. Because the specific alloying material 114 chosen may not have thecorrect crystalline structure to serve as a seed for copper plating, abottom-up plating technique, free of voiding or pinch-off, may thereforebe achieved. The bottom-up plating technique results in filling theopening 106 (shown in FIG. 1C) with the copper material 116. After theelectroplating technique a chemical mechanical polishing (CMP) techniquemay be used to remove excess copper from the surface of the substrate.The CMP technique can remove the diffusion barrier 112, the alloyingmaterial 114, and excess copper material 116 selective to the topsurface of the nonmetallic material 102.

The alloying material 114 may be used to form a mechanical bond betweenthe copper material 116 and the sidewall 109 of the opening 106. Themechanical bond can be created either by forming an intermetalliccompound or by creating a high friction interface caused by an extremelyclose contact between layers. Extremely close contact may be defined asmaximizing interfacial surface contact while minimizing foreigncontaminants between two layers. The mechanical bond may be created atan intersection 124 or an intersection 126. Lack of a mechanical bondbetween the copper material 116 and the sidewall 109 of the opening 106may result in a pistoning effect where the copper material 116 movesvertically within the opening 106 during thermal cycling due to copper'srelatively high coefficient of thermal expansion in comparison tosurrounding semiconductor materials (e.g. silicon, silicon oxides, andsilicon nitrides). Thermal expansion and contraction is inevitable whenbuilding or operating integrated circuits. Pistoning of the coppermaterial 116 may impose stress and strain on corresponding componentsthat may be connected to the copper material 116 and over time willcause a failure in these connections.

Referring to FIGS. 2-6, multiple different embodiments of theinterconnect structure 100 are shown. Now referring to FIG. 2, oneembodiment of the interconnect structure 100 is shown. A firstinteraction may occur between the alloying material 114 (shown in FIG.1D) and the copper material 116 at the intersection 124 (shown in FIG.1D). The first interaction may produce a first intermetallic compound118 formed from the alloying material 114 (shown in FIG. 1D) and thecopper material 116 at the intersection 124 (shown in FIG. 1D). Thefirst intermetallic compound 118 may include the alloying material 114(shown in FIG. 1D) and the copper material 116. The first intermetalliccompound 118 can form a mechanical bond between the alloying material114 (shown in FIG. 1D) and the copper material 116. The firstintermetallic compound 118 may be formed either simultaneously whileplating the copper material 116 or any time thereafter, for exampleduring a subsequent annealing process.

Formation of the intermetallic compound 118 between the alloyingmaterial 114 (shown in FIG. 1D) and the copper material 116 may occurwhen favorable thermodynamic and kinetic conditions exist for thecompounds to form as a precipitate within a solid solution of the twomaterials, in this case the alloying material 114 (shown in FIG. 1D) andthe copper material 116. Intermetallic compounds may be stoichiometricor non-stoichiometric. For example, Ag₃Sn is an intermetallic compoundthat may form when Ag and Sn are in a solid solution.

A second interaction may occur between the diffusion barrier 112 and thealloying material 114 (shown in FIG. 1D) at the intersection 126 (shownin FIG. 1D). The second interaction may involve extremely close contactbetween the diffusion barrier 112 and the alloying material 114 (shownin FIG. 1D) at the intersection 126 (shown in FIG. 1D). Extremely closecontact may create an area of high friction which may result in amechanical bond between the diffusion barrier 112 and the alloyingmaterial 114 (shown in FIG. 1D). In one embodiment, extremely closecontact may be achieved by depositing one material on top of anothermaterial in a vacuum using a sputter deposition technique. If onematerial is deposited on another material with either vacuuminterruption or via an aqueous system, the possibility for extremelyclose contact is significantly diminished by native oxides or third bodyinterference films, e.g. water may be present between the interfaces.The alloying material 114 (shown in FIG. 1D) may be deposited on top ofthe diffusion barrier 112 in a vacuum using the sputter depositiontechnique, and resulting in extremely close contact.

With continued reference to FIG. 2, the diffusion barrier 112 may bedeposited with uniform, or near uniform, thickness. The firstintermetallic compound 118 may have a non-uniform thickness and canmechanically join the alloying material 114 (shown in FIG. 1D) with thecopper material 116. Formation of the first intermetallic compound 118may consume all or some of the alloying material 114 (shown in FIG. 1D).In one embodiment, the alloying material 114 (shown in FIG. 1D) isentirely consumed by the formation of the first intermetallic compound118, as shown in FIG. 2. The mechanical bond created by the firstintermetallic compound 118 and extremely close contact between thediffusion barrier 112 and the alloying material 114 (shown in FIG. 1D)can minimize the pistoning effect described above. The integrity of chipinterconnects can be greatly improved by minimizing the pistoning effectbecause of the reduced risk of interconnect failure due to thermalexpansion and contraction.

Now referring to FIG. 3, one embodiment of the interconnect structure100 is shown. A first interaction may occur between the alloyingmaterial 114 and the copper material 116 at the intersection 124 (shownin FIG. 1D). The first interaction may produce the first intermetalliccompound 118 formed from the alloying material 114 and the coppermaterial 116 at the intersection 124 (shown in FIG. 1D). The firstintermetallic compound 118 may include the alloying material 114 and thecopper material 116. The first intermetallic compound 118 can form amechanical bond between the alloying material 114 and the coppermaterial 116. The first intermetallic compound 118 may be formed eithersimultaneously while plating the copper material 116 or any timethereafter, for example during a subsequent annealing process.

A second interaction may occur between the diffusion barrier 112 and thealloying material 114 at the intersection 126. The second interactionmay involve extremely, close contact between the diffusion barrier 112and the alloying material 114 at the intersection 126. Extremely closecontact may create an area of high friction which may result in amechanical bond between the diffusion barrier 112 and the alloyingmaterial 114.

With continued reference to FIG. 3, the diffusion barrier 112 may bedeposited with uniform, or near uniform, thickness. The firstintermetallic compound 118 may have a non-uniform thickness and canmechanically join the alloying material 114 with the copper material116. Formation of the first intermetallic compound 118 may consume allor some of the alloying material 114. In one embodiment, the alloyingmaterial 114 is not entirely consumed by the formation of the firstintermetallic compound 118 such that some of the alloying material 114remains between the first intermetallic compound 118 and the diffusionbarrier 112, as shown in FIG. 3. The mechanical bond created by thefirst intermetallic compound 118 and extremely close contact between thediffusion barrier 112 and the alloying material 114 can minimize thepistoning effect described above. The integrity of chip interconnectscan be greatly improved by minimizing the pistoning effect because ofthe reduced risk of interconnect failure due to thermal expansion andcontraction.

Now referring to FIG. 4, one embodiment of the interconnect structure100 is shown. A first interaction may occur between the alloyingmaterial 114 (shown in FIG. 1D) and the copper material 116 at theintersection 124 (shown in FIG. 1D). The first interaction may producethe first intermetallic compound 118 formed from the alloying material114 (shown in FIG. 1D) and the copper material 116 at the intersection124 (shown in FIG. 1D). The first intermetallic compound 118 may includethe alloying material 114 (shown in FIG. 1D) and the copper material116. The first intermetallic compound 118 can form a mechanical bondbetween the alloying material 114 (shown in FIG. 1D) and the coppermaterial 116. The first intermetallic compound 118 may be formed eithersimultaneously while plating the copper material 116 or any timethereafter, for example during a subsequent annealing process.

A second interaction may occur between the diffusion barrier 112 and thealloying material 114 (shown in FIG. 1D) at the intersection 126 (shownin FIG. 1D). The second interaction may produce a second intermetalliccompound 120 formed from the diffusion barrier 112 and the alloyingmaterial 114 (shown in FIG. 1D) at the intersection 126 (shown in FIG.1D). The second intermetallic compound 120 may include the diffusionbarrier 112 and the alloying material 114 (shown in FIG. 1D). The secondintermetallic compound 120 can form a mechanical bond between thediffusion barrier 112 and the alloying material 114 (shown in FIG. 1D).The second intermetallic compound 120 may be formed eithersimultaneously while depositing the alloying material 114 (shown in FIG.1D) or any time thereafter, for example during a subsequent annealingprocess.

With continued reference to FIG. 4, the diffusion barrier 112 may bedeposited with uniform, or near uniform, thickness. The firstintermetallic compound 118 may have a non-uniform thickness and canmechanically join the alloying material 114 (shown in FIG. 1D) with thecopper material 116. The second intermetallic compound 120 may have anon-uniform thickness and can mechanically join the diffusion barrier112 with the alloying material 114 (shown in FIG. 1D). Formation of theintermetallic compounds 118, 120 may consume all or some of the alloyingmaterial 114 (shown in FIG. 1D). In one embodiment, the alloyingmaterial 114 (shown in FIG. 1D) is entirely consumed by the formation ofthe intermetallic compounds 118, 120, as shown in FIG. 4. The mechanicalbond created by the intermetallic compounds 118, 120 can minimize thepistoning effect described above. The integrity of chip interconnectscan be greatly improved by minimizing the pistoning effect because ofthe reduced risk of interconnect failure due to thermal expansion andcontraction.

Now referring to FIG. 5, one embodiment of the interconnect structure100 is shown. A first interaction may occur between the alloyingmaterial 114 and the copper material 116 at the intersection 124 (shownin FIG. 1D). The first interaction may produce the first intermetalliccompound 118 formed from the alloying material 114 and the coppermaterial 116 at the intersection 124 (shown in FIG. 1D). The firstintermetallic compound 118 may include the alloying material 114 and thecopper material 116. The first intermetallic compound 118 can form amechanical bond between the alloying material 114 and the coppermaterial 116. The first intermetallic compound 118 may be formed eithersimultaneously while plating the copper material 116 or any timethereafter, for example during a subsequent annealing process.

A second interaction may occur between the diffusion barrier 112 and thealloying material 114 at the intersection 126 (shown in FIG. 1D). Thesecond interaction may produce the second intermetallic compound 120formed from the diffusion barrier 112 and the alloying material 114 atthe intersection 126 (shown in FIG. 1D). The second intermetalliccompound 120 may include the diffusion barrier 112 and the alloyingmaterial 114. The second intermetallic compound 120 can form amechanical bond between the diffusion barrier 112 and the alloyingmaterial 114. The second intermetallic compound 120 may be formed eithersimultaneously while depositing the alloying material 114 or any timethereafter, for example during a subsequent annealing process.

With continued reference to FIG. 5, the diffusion barrier 112 may bedeposited with uniform, or near uniform, thickness. The firstintermetallic compound 118 may have a non-uniform thickness and canmechanically join the alloying material 114 with the copper material116. The second intermetallic compound 120 may have a non-uniformthickness and can mechanically join the diffusion barrier 112 with thealloying material 114. Formation of the intermetallic compounds 118, 120may consume all or some of the alloying material 114. In one embodiment,the alloying material 114 is not entirely consumed by the formation ofthe intermetallic compounds 118, 120 such that some of the alloyingmaterial 114 remains between the first intermetallic compound 118 andthe second intermetallic compound 120, as shown in FIG. 5. Themechanical bond created by the intermetallic compounds 118, 120 canminimize the pistoning effect described above. The integrity of chipinterconnects can be greatly improved by minimizing the pistoning effectbecause of the reduced risk of interconnect failure due to thermalexpansion and contraction.

Now referring to FIG. 6, one embodiment of the interconnect structure100 is shown. A first interaction may occur between the alloyingmaterial 114 and the copper material 116 at the intersection 124 (shownin FIG. 1D). The first interaction may produce the first intermetalliccompound 118 formed from the alloying material 114 and the coppermaterial 116 at the intersection 124 (shown in FIG. 1D). The firstintermetallic compound 118 may include the alloying material 114 and thecopper material 116. The first intermetallic compound 118 can form amechanical bond between the alloying material 114 and the coppermaterial 116. The first intermetallic compound 118 may be formed eithersimultaneously while plating the copper material 116 or any timethereafter, for example during a subsequent annealing process.

A second interaction may occur between the diffusion barrier 112 and thealloying material 114 at the intersection 126. The second interactionmay involve extremely, close contact between the diffusion barrier 112and the alloying material 114 at the intersection 126. Extremely closecontact may create an area of high friction which may result in amechanical bond between the diffusion barrier 112 and the alloyingmaterial 114.

The optional electrically insulating liner 110 may be deposited on topof the nonmetallic material 102 and not on the conductive pad 104 priorto depositing the diffusion barrier 112. In one embodiment, theelectrically insulating liner 110 may be deposited on the sidewall 109and the bottom 108 of the opening 106. In such embodiments theelectrically insulating liner 110, along with the diffusion barrier 112and the alloying material 114, may be subsequently removed from thebottom 108 of the opening 106. For example, an anisotropic etch may beused to remove the electrically insulating liner 110, the diffusionbarrier 112, and the alloying material 114 from the bottom 108 to exposethe conductive pad 104 without removing material from the sidewall ofthe opening 106. Alternatively, the anisotropic etch may be performed toremove each of the deposited layers from the bottom 108 of the opening106 immediately following their deposition.

The electrically insulating liner 110 may include any material thatwhich prohibits the conduction of electricity between a copper materialand a semi-conductive nonmetallic material. Therefore, if thenonmetallic material 102 is itself electrically insulating, theelectrically insulating liner 110 may not be used. The electricallyinsulating liner 110 may be made from an oxide, nitride, or insulatingpolymer. Deposition techniques such as, for example, chemical vapordeposition (CVD), physical vapor deposition (PVD), or atomic layerdeposition (ALD), may be used to deposit the electrically insulatingliner 110.

With continued reference to FIG. 6, the diffusion barrier 112 may bedeposited on top of the electrically insulating liner 110 with uniform,or near uniform, thickness. The first intermetallic compound 118 mayhave a non-uniform thickness and can mechanically join the alloyingmaterial 114 with the copper material 116. Formation of the firstintermetallic compound 118 may consume all or some of the alloyingmaterial 114. In one embodiment, the alloying material 114 is notentirely consumed by the formation of the first intermetallic compound118 such that some of the alloying material 114 remains between thefirst intermetallic compound 118 and the diffusion barrier 112, as shownin FIG. 6. The mechanical bond created by the first intermetalliccompound 118 and extremely close contact between the diffusion barrier112 and the alloying material 114 can minimize the pistoning effectdescribed above. The integrity of chip interconnects can be greatlyimproved by minimizing the pistoning effect because of the reduced riskof interconnect failure due to thermal expansion and contraction.

Referring to FIGS. 7A-7E, multiple steps of a method of forming a copperinterconnect structure are shown. Now referring to FIG. 7A, across-sectional view of an interconnect structure 200 having an opening206 in a nonmetallic material 202. The interconnect structure 200 mayinclude lines or wires. In one embodiment, the nonmetallic material 202may be made from any of several known semiconductor materials such as,for example, a bulk silicon substrate. Non-limiting examples includesilicon, germanium, silicon-germanium alloy, silicon carbide,silicon-germanium carbide alloy, and compound (e.g. III-V and II-VI)semiconductor materials. In one embodiment, the nonmetallic material 202may be made from a dielectric material know to a person having ordinaryskill in the art. An optional electrically insulating liner (not shown)may be deposited along a sidewall 209 and on top of the nonmetallicmaterial 202 within the opening 206.

Now referring to FIG. 7B, a diffusion barrier 212 may be deposited alongthe sidewall 209 and on top of the nonmetallic material 202. Thediffusion barrier 212 may be deposited along the sidewall 209 and abottom 208 of the opening 206. The diffusion barrier 212 may include anymaterial that which prohibits contamination of a copper material by thenonmetallic material 202. In one embodiment, the diffusion barrier 212may be made from a material including tantalum nitride deposited byphysical vapor deposition (PVD). In one embodiment, the diffusionbarrier 212 may be deposited by an alternative deposition technique, forexample chemical vapor deposition (CVD) or atomic layer deposition(ALD).

Now referring to FIG. 7C, a seed layer 222 may be deposited on top ofthe diffusion barrier 212 and along the sidewall 209 and the bottom 208of the opening 206. In one embodiment, the seed layer 222 may be madeform a material including copper or any other element capable of seedingcopper, i.e. having the correct crystalline structure to seed copper. Inother words, the crystal face orientation of the seed layer 222 willmimic the crystal face orientation of copper; such that the surface ofthe seed layer 222 will allow copper to grow from the its face. In oneembodiment, the seed layer 222 may be made from a material includingcopper and deposited by PVD. In one embodiment, the seed layer 222 maybe deposited by CVD or ALD.

Now referring to FIG. 7D, an alloying material 214 may be deposited ontop of the seed layer 222, but only along the sidewall 209 of theopening 206. In one embodiment, the alloying material 214 may bedeposited along the sidewall 209 and the bottom 208 of the opening 206.In such embodiments the alloying material 214 may be subsequentlyremoved from the bottom 208 only by using an anisotropic etch techniqueselective to the seed layer 222. In one embodiment, the alloyingmaterial 214 may be made from a material including chromium deposited ina vacuum using a sputter deposition technique. In one embodiment, thealloying material 214 may be made from a material including chromium,copper, nickel, tin, magnesium, cobalt, aluminum, manganese, titanium,zirconium, indium, palladium, gold or some combination thereof. Thealloying material 214 may not have the correct crystalline structure toserve as a seed for copper plating. In one embodiment, an optionaladhesive liner 228 such as gold (see FIG. 14) may be used prior todepositing the alloying material 214. The thickness of the alloyingmaterial 214 may be between 50 to about 300 angstroms.

Now referring to FIG. 7E, a copper material 216 may be deposited on theseed layer 222 and within the opening 206 (shown in FIG. 7D) using anelectroplating technique. The seed layer 222 may serve as a cathode towhich an electrical potential is applied during an electroplatingtechnique. Specifically, a negative voltage is applied to the seed layer222. Because the specific alloying material 214 chosen may not have thecorrect crystalline structure to serve as a seed for copper plating, abottom-up plating technique, free of voiding or pinch-off, may thereforebe achieved. The bottom-up plating technique results in filling theopening 206 (shown in FIG. 7D) with the copper material 216. After theelectroplating technique a chemical mechanical polishing (CMP) techniquemay be used to remove excess copper from the surface of the substrate.The CMP technique can remove the diffusion barrier 212, the seed layer222, the alloying material 214, and excess copper material 216 selectiveto the top surface of the nonmetallic material 202.

The alloying material 214 may be used to form a mechanical bond betweenthe copper material 216 and the sidewall 209 of the opening 206. Themechanical bond can be created either by forming an intermetalliccompound or by creating a high friction interface caused by extremelyclose contact between layers. Extremely close contact may be defined asmaximizing interfacial surface contact while minimizing foreigncontaminants between two layers. The mechanical bond may be created atan intersection 224 and an intersection 226. Lack of a mechanical bondbetween the copper material 216 and the sidewall 209 of the opening 206may result in a pistoning effect where the copper material 216 movesvertically within the opening 206 during thermal cycling due to copper'srelatively high coefficient of thermal expansion in comparison tosurrounding semiconductor materials (e.g. silicon, silicon oxides, andsilicon nitrides). Thermal expansion and contraction is inevitable whenbuilding or operating integrated circuits. Pistoning of the coppermaterial 216 may impose stress and strain on corresponding componentsthat may be connected to the copper material 216 and over time willcause a failure in these connections.

Referring to FIGS. 8-12, multiple different embodiments of theinterconnect structure 200 are shown. Now referring to FIG. 8, oneembodiment of the interconnect structure 200 is shown. A firstinteraction may occur between the alloying material 214 (shown in FIG.7E) and the copper material 216 at the intersection 224 (shown in FIG.7E). The first interaction may produce a first intermetallic compound218 formed from the alloying material 214 (shown in FIG. 7E) and thecopper material 216 at the intersection 224 (shown in FIG. 7E). Thefirst intermetallic compound 218 may include the alloying material 214(shown in FIG. 7E) and the copper material 216. The first intermetalliccompound 218 can form a mechanical bond between the alloying material214 (shown in FIG. 7E) and the copper material 216. The firstintermetallic compound 218 may be formed either simultaneously whileplating the copper material 216 or any time thereafter, for exampleduring a subsequent annealing process.

Formation of the intermetallic compound 218 between the alloyingmaterial 214 (shown in FIG. 7E) and the copper material 216 may occurwhen favorable thermodynamic and kinetic conditions exist for thecompounds to form as a precipitate within a solid solution of the twomaterials, in this case the alloying material 214 (shown in FIG. 7E) andthe copper material 216. Intermetallic compounds may be stoichiometricor non-stoichiometric. For example, Ag₃Sn is an intermetallic compoundthat may form when Ag and Sn are in a solid solution.

A second interaction may occur between the diffusion barrier 212 and theseed layer 222 at the intersection 226. The second interaction mayinvolve extremely close contact between the seed layer 222 and thealloying material 214 (shown in FIG. 7E) at the intersection 226 (shownin FIG. 7E). Extremely close contact may create an area of high frictionwhich may result in a mechanical bond between the seed layer 222 and thealloying material 214 (shown in FIG. 7E). Extremely close contact may beachieved by depositing one material on top of another material in avacuum using a sputter deposition technique. If one material isdeposited on another material with either vacuum interruption or via anaqueous system, the possibility for extremely close contact issignificantly diminished by native oxides or third body interferencefilms, e.g. water may be present between the interfaces. The seed layer222 may be deposited on top of the diffusion barrier 112 in a vacuumusing the sputter deposition technique, and resulting in an extremelyclose physical interface.

With continued reference to FIG. 8, the diffusion barrier 212 may bedeposited with uniform, or near uniform, thickness. The seed layer 222may be deposited with uniform, or near uniform, thickness. The firstintermetallic compound 218 may have a non-uniform thickness and canmechanically join the alloying material 214 (shown in FIG. 7E) with thecopper material 216. Formation of the first intermetallic compound 218may consume all or some of the alloying material 214 (shown in FIG. 7E).In one embodiment, the alloying material 214 (shown in FIG. 7E) isentirely consumed by the formation of the first intermetallic compound218, as shown in FIG. 8. The mechanical bond created by the firstintermetallic compound 218 and extremely close contact between the seedlayer 222 and the alloying material 214 (shown in FIG. 7E) can minimizethe pistoning effect described above. The integrity of chipinterconnects can be greatly improved by minimizing the pistoning effectbecause of the reduced risk of interconnect failure due to thermalexpansion and contraction.

Now referring to FIG. 9, one embodiment of the interconnect structure200 is shown. A first interaction may occur between the alloyingmaterial 214 and the copper material 216 at the intersection 224 (shownin FIG. 7E). The first interaction may produce a first intermetalliccompound 218 formed from the alloying material 214 and the coppermaterial 216 at the intersection 224 (shown in FIG. 7E). The firstintermetallic compound 218 may include the alloying material 214 and thecopper material 216. The first intermetallic compound 218 can form amechanical bond between the alloying material 214 and the coppermaterial 216. The first intermetallic compound 218 may be formed eithersimultaneously while plating the copper material 216 or any timethereafter, for example during a subsequent annealing process.

A second interaction may occur between the seed layer 222 and thealloying material 214 at the intersection 226. The second interactionmay involve extremely, close contact between the seed layer 222 and thealloying material 214 at the intersection 226. Extremely close contactmay create an area of high friction which may result in a mechanicalbond between the seed layer 222 and the alloying material 214.

With continued reference to FIG. 9, the diffusion barrier 212 may bedeposited with uniform, or near uniform, thickness. The seed layer 222may be deposited with uniform, or near uniform, thickness. The firstintermetallic compound 218 may have a non-uniform thickness and canmechanically join the alloying material 214 with the copper material216. Formation of the first intermetallic compound 218 may consume allor some of the alloying material 214. In one embodiment, the alloyingmaterial 214 is not entirely consumed by the formation of the firstintermetallic compound 218 such that some of the alloying material 214remains between the first intermetallic compound 218 and the seed layer222, as shown in FIG. 9. The mechanical bond created by the firstintermetallic compound 218 and extremely close contact between the seedlayer 222 and the alloying material 214 can minimize the pistoningeffect described above. The integrity of chip interconnects can begreatly improved by minimizing the pistoning effect because of thereduced risk of interconnect failure due to thermal expansion andcontraction.

Now referring to FIG. 10, one embodiment of the interconnect structure200 is shown. A first interaction may occur between the alloyingmaterial 214 (shown in FIG. 7E) and the copper material 216 at theintersection 224 (shown in FIG. 7E). The first interaction may produce afirst intermetallic compound 218 formed from the alloying material 214(shown in FIG. 7E) and the copper material 216 at the intersection 224(shown in FIG. 7E). The first intermetallic compound 218 may include thealloying material 214 (shown in FIG. 7E) and the copper material 216.The first intermetallic compound 218 can form a mechanical bond betweenthe alloying material 214 (shown in FIG. 7E) and the copper material216. The first intermetallic compound 218 may be formed eithersimultaneously while plating the copper material 216 or any timethereafter, for example during a subsequent annealing process.

A second interaction may occur between the seed layer 222 and thealloying material 214 (shown in FIG. 7E) at the intersection 226 (shownin FIG. 7E). The second interaction may produce a second intermetalliccompound 220 formed from the seed layer 222 and the alloying material214 (shown in FIG. 7E) at the intersection 226 (shown in FIG. 7E). Thesecond intermetallic compound 220 may include the seed layer 222 and thealloying material 214 (shown in FIG. 7E). The second intermetalliccompound 220 can form a mechanical bond between the seed layer 222 andthe alloying material 214 (shown in FIG. 7E). The second intermetalliccompound 220 may be formed either simultaneously while depositing thealloying material 214 (shown in FIG. 7E) or any time thereafter, forexample during a subsequent annealing process.

With continued reference to FIG. 10 the diffusion barrier 212 may bedeposited with uniform, or near uniform, thickness. The seed layer 222may be deposited with uniform, or near uniform, thickness. The firstintermetallic compound 218 may have a non-uniform thickness and canmechanically join the alloying material 214 (shown in FIG. 7E) with thecopper material 216. The second intermetallic compound 220 may have anon-uniform thickness and can mechanically join the seed layer 222 withthe alloying material 214 (shown in FIG. 7E). Formation of theintermetallic compounds 218, 220 may consume all or some of the alloyingmaterial 214 (shown in FIG. 7E). In one embodiment, the alloyingmaterial 214 (shown in FIG. 7E) is entirely consumed by the formation ofthe intermetallic compounds 218, 220, as shown in FIG. 10. Themechanical bond created by the intermetallic compounds 218, 220 canminimize the pistoning effect described above. The integrity of chipinterconnects can be greatly improved by minimizing the pistoning effectbecause of the reduced risk of interconnect failure due to thermalexpansion and contraction.

Now referring to FIG. 11, one embodiment of the interconnect structure200 is shown. A first interaction may occur between the alloyingmaterial 214 and the copper material 216 at the intersection 224 (shownin FIG. 7E). The first interaction may produce a first intermetalliccompound 218 formed from the alloying material 214 and the coppermaterial 216 at the intersection 224 (shown in FIG. 7E). The firstintermetallic compound 218 may include the alloying material 214 and thecopper material 216. The first intermetallic compound 218 can form amechanical bond between the alloying material 214 and the coppermaterial 216. The first intermetallic compound 218 may be formed eithersimultaneously while plating the copper material 216 or any timethereafter, for example during a subsequent annealing process.

A second interaction may occur between the seed layer 222 and thealloying material 214 at the intersection 226 (shown in FIG. 7E). Thesecond interaction may produce the second intermetallic compound 220formed from the seed layer 222 and the alloying material 214 at theintersection 226 (shown in FIG. 7E). The second intermetallic compound220 may include the seed layer 222 and the alloying material 214. Thesecond intermetallic compound 220 can form a mechanical bond between theseed layer 222 and the alloying material 214. The second intermetalliccompound 220 may be formed either simultaneously while depositing thealloying material 114 or any time thereafter, for example during asubsequent annealing process.

With continued reference to FIG. 11, the diffusion barrier 212 may bedeposited with uniform, or near uniform, thickness. The seed layer 222may be deposited with uniform, or near uniform, thickness. The firstintermetallic compound 218 may have a non-uniform thickness and canmechanically join the alloying material 214 with the copper material216. The second intermetallic compound 220 may have a non-uniformthickness and can mechanically join the seed layer 222 with the alloyingmaterial 214. Formation of the intermetallic compounds 218, 220 mayconsume all or some of the alloying material 214. In one embodiment, thealloying material 214 is not entirely consumed by the formation of theintermetallic compounds 218, 220 such that some of the alloying material214 remains between the first intermetallic compound 218 and the secondintermetallic compound 220 as shown in FIG. 11. The mechanical bondcreated by the intermetallic compounds 218, 220 can minimize thepistoning effect described above. The integrity of chip interconnectscan be greatly improved by minimizing the pistoning effect because ofthe reduced risk of interconnect failure due to thermal expansion andcontraction.

Now referring to FIG. 12, one embodiment of the interconnect structure200 is shown. A first interaction may occur between the alloyingmaterial 214 and the copper material 216 at the intersection 224 (shownin FIG. 7E). The first interaction may produce a first intermetalliccompound 218 formed from the alloying material 214 and the coppermaterial 216 at the intersection 224 (shown in FIG. 7E). The firstintermetallic compound 218 may include the alloying material 214 and thecopper material 216. The first intermetallic compound 218 can form amechanical bond between the alloying material 214 and the coppermaterial 116. The first intermetallic compound 218 may be formed eithersimultaneously while plating the copper material 216 or any timethereafter, for example during a subsequent annealing process.

A second interaction may occur between the seed layer 222 and thealloying material 214 at the intersection 226. The second interactionmay involve extremely, close contact between the seed layer 222 and thealloying material 214 at the intersection 226. Extremely close contactmay create an area of high friction which may result in a mechanicalbond between the seed layer 222 and the alloying material 214.

The optional electrically insulating liner 210 may be deposited on topof the nonmetallic material 202 prior to depositing the diffusionbarrier 212. The electrically insulating liner 210 may include anymaterial that which prohibits the conduction of electricity between acopper material and a semi-conductive nonmetallic material. Therefore,if the nonmetallic material 202 is itself electrically insulating, theelectrically insulating liner 210 may not be used. The electricallyinsulating liner 210 may be made from an oxide, nitride, or insulatingpolymer. Deposition techniques such as, for example, chemical vapordeposition (CVD), physical vapor deposition (PVD), or atomic layerdeposition (ALD), may be used to deposit the electrically insulatingliner 210.

With continued reference to FIG. 12, the diffusion barrier 212 may bedeposited on top of the electrically insulating liner 210 with uniform,or near uniform, thickness. The first intermetallic compound 218 mayhave a non-uniform thickness and can mechanically join the alloyingmaterial 214 with the copper material 216. Formation of the firstintermetallic compound 218 may consume all or some of the alloyingmaterial 214. In one embodiment, the alloying material 214 is notentirely consumed by the formation of the first intermetallic compound218 such that some alloying material 214 remains between the firstintermetallic compound 218 and the seed layer 222, as shown in FIG. 12.The mechanical bond created by the first intermetallic compound 218 andextremely close contact between the seed layer 222 and the alloyingmaterial 214 can minimize the pistoning effect described above. Theintegrity of chip interconnects can be greatly improved by minimizingthe pistoning effect because of the reduced risk of interconnect failuredue to thermal expansion and contraction.

The descriptions of the various embodiments of the present inventionhave been presented for purposes of illustration, but are not intendedto be exhaustive or limited to the embodiments disclosed. Manymodifications and variations will be apparent to those of ordinary skillin the art without departing from the scope and spirit of the describedembodiments. The terminology used herein was chosen to best explain theprinciples of the embodiment, the practical application or technicalimprovement over technologies found in the marketplace, or to enableother of ordinary skill in the art to understand the embodimentsdisclosed herein.

What is claimed is:
 1. A method of plating a structure comprising anopening etched in a nonmetallic material, a diffusion barrier depositedalong a sidewall of the opening, and a conductive pad located at abottom of the opening, the method comprising: depositing an alloyinglayer along the sidewall of the opening and in direct contact with thediffusion barrier, wherein the alloying layer comprises a crystallinestructure that cannot serve as a seed for plating a conductive material;exposing the opening to an electroplating solution comprising theconductive material, wherein the conductive material is not present inthe alloying layer; applying an electrical potential to a cathodecausing the conductive material to deposit from the electroplatingsolution onto the cathode, and causing the opening to fill with theconductive material, wherein the cathode comprises the conductive padand excludes the alloying layer; and forming a first intermetalliccompound along an intersection of the alloying layer and the conductivematerial, the first intermetallic compound is formed as a precipitatewithin a solid solution of the alloying layer and the conductivematerial.
 2. The method of claim 1, further comprising: forming a secondintermetallic compound along an intersection between the diffusionbarrier and the alloying material, the second intermetallic compoundcomprising the diffusion barrier and the alloying material.
 3. Themethod of claim 1, wherein depositing the alloying layer comprisesdepositing chromium.
 4. The method of claim 1, wherein depositing thealloying layer comprises depositing at least one of the materialsselected from the group consisting of chromium, tin, nickel, magnesium,cobalt, aluminum, manganese, titanium, zirconium, indium, palladium, andsilver.
 5. The method of claim 1, wherein the conductive pad comprisescopper.
 6. The method of claim 1, wherein depositing the conductivematerial comprises depositing a material selected from the groupconsisting of copper, aluminum, and tungsten.
 7. The method of claim 1,further comprising: depositing an electrically insulating liner alongthe sidewall of the opening between the nonmetallic material and thediffusion barrier.
 8. The method of claim 1, further comprising:depositing a gold liner along the sidewall of the opening adjacent toand in direct contact with the diffusion barrier before depositing thealloying layer.